A known vehicle steering apparatus includes a front steering gear connected with front steerable wheels of a vehicle. Two rear steering gears are connected with rear steerable wheels of the vehicle. A position sensor determines the steering position of front steerable wheels of the vehicle. A controller controls operation of the two rear steering gears and turning of the rear steerable wheels of the vehicle. A steering apparatus having this construction is disclosed in U.S. Pat. No. 6,945,350.
Another known vehicle steering apparatus includes a front steering gear connected with front steerable wheels of a vehicle. A rear steering gear may be connected with rear steerable wheels of a vehicle. A torque sensor is connected with a steering wheel of the vehicle, and a controller is connected with the torque sensor. The torque sensor is operable to provide an output upon manual application of force to the steering wheel. The controller is operable to effect operation of the rear steering gear in response to the output from the torque sensor indicating application of at least a predetermined force to the steering wheel. A steering apparatus having this construction is disclosed in U.S. Patent Application Publication No. 2007/0144818.